00:01
In this problem, we're being asked to find the sum of the first 14 terms in the given arithmetic series.
00:05
So we have a formula to help us do this.
00:08
It says that in order to find s of b is equal to n over 2 times the quantity of 2 times a sub 1 plus d times a minus 1.
00:18
Well, if you recall, a sub 1 is the first term in the series.
00:21
In this case, that would be 11.
00:24
D is our common difference, meaning how do we get from one term to the next? well, we keep adding negative 4.
00:30
So d is negative 4.
00:32
And because we're trying to find the sum of the first 14 terms and is equal to 14.
00:37
So now that we have these three values, we can substitute them into our formula...